Since manufacturing of circuits is costly, it is desirable to test the circuit design prior to manufacturing to ensure that a circuit will operate correctly. For example, circuit simulations may be performed on a circuit design to determine currents and voltages at various nodes within the circuit design. In order to perform circuit simulations on circuit designs, though, the circuit simulator needs access to circuit models of the various elements within the circuit design. That is, a circuit model provides a representation of a physical circuit element by describing its structure and operation. These circuit models may, in the ease of complex circuit elements, be simplified representations of the physical element. However, oversimplified circuit models, while reducing design and test time, may result in inaccurate testing results. For example, simulations of Magnetoresistive Tunnel Junction (MJT) MRAMs available today use simple resistors to model the resistance within the MRAMs, thus not taking into account the nonlinear effects of the resistance. Furthermore, the simulations of MRAMs available today do not take into account the actual switching of the memory. This oversimplified model leads to errors in the circuit design. Therefore, there is a need for an improved circuit model for MRAMs which models both the switching of the MTJ and the different non-linear tunnel junction resistances in both states of the memory in order to improve simulation of MRAMs.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of the embodiments of the present invention.